Geotechnical Field Work Nearly Complete

Geotechnical Field Work Nearly Complete

The field work component of an extensive geotechnical investigation programme for the proposed Project Aqua hydro-electric scheme is nearly complete.

The geotechnical programme aims to improve the understanding of the geology of the lower Waitaki Valley.

The proposed Project Aqua hydro-electric scheme would run along the south side of the Valley. It would generate enough low-cost, renewable electricity to power the equivalent of about 375,000 households in an average year and about 250,000 households in a very dry year. A very dry year is a 1-in-20 year event.

Meridian Energy Civil Investigations Manager Sigi Keis says the information gained from the geotechnical work is being used to update a detailed longitudinal section of the full length of the proposed canal route.

“The work has gone very smoothly. We have drilled 240 holes – each down to a depth of between 15 and 60 metres with a 100 millimetre diameter bit, and we have used excavators of different capacity to dig 430 test pits – each 3 to 5 metres deep,” says Sigi Keis.

The field work aims to identify the types and properties of gravels and the underlying rock formations. The holes and test pits will also provide records of the groundwater levels in the lower Waitaki Valley which can be expected to be encountered during construction.

“This information is needed for the detailed design of Project Aqua and to help with cost estimates for the proposed scheme,” says Sigi Keis. “It will allow confirmation of the conceptual design including the location of power stations and the canal.”

In addition to the field investigations carried out along the canal corridor, four potential quarry sites are being investigated as a possible source to provide a considerable quantity of armour rock required for the scheme. Laboratory testing by CTS (Central Testing Services, Alexandra) is being carried out on samples taken during field investigations. The testing will determine the properties and suitability of the gravels along the canal corridor and the soils in the six borrow areas that are proposed for lining and filters for the construction of the Project Aqua canal.

While the majority of the laboratory results have been processed already, testing is expected to be completed are by mid-February 2004.

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